Handheld physiological sensor

Abstract

A handheld device measures all vital signs and some hemodynamic parameters from the human body and transmits measured information wirelessly to a web-based system, where the information can be analyzed by a clinician to help diagnose a patient. The system utilizes our discovery that bio-impedance signals used to determine vital signs and hemodynamic parameters can be measured over a conduction pathway extending from the patient's wrist to a location on their thoracic cavity, e.g. their chest or navel. The device's form factor can include re-usable electrode materials to reduce costs. Measurements made by the handheld device, which use the belly button as a ‘fiducial’ marker, facilitate consistent, daily measurements, thereby reducing positioning errors that reduce accuracy of standard impedance measurements. In this and other ways, the handheld device provides an effective tool for characterizing patients with chronic diseases, such as heart failure, renal disease, and hypertension.

Description

BACKGROUND AND FIELD OF THE INVENTION[0001]1. Field of the Invention[0002]The invention relates to sensors that measure physiological signals from patients, and the use of such sensors.[0003]2. General Background[0004]Physiological sensors, such as vital sign monitors, typically measure signals from a patient to determine time-varying waveforms, e.g. thoracic bio-impedance (TBI), bio-reactance (BR), and electrocardiogram (ECG) waveforms, with electrodes that attach to the patient's skin. These waveforms can be processed / analyzed to extract other medically relevant parameters such as heart rate (HR) and heart rate variability (HRV), respiration rate (RR), stroke volume (SV), cardiac output (CO), and information relating to thoracic fluids, e.g. thoracic fluid index (TFC) and general body fluids (FLUIDS). Certain physiological conditions can be identified from these parameters using one-time measurements; other conditions require observation of time-dependent trends in the parameters ...

AI Technical Summary

Benefits of technology

[0025]In view of the foregoing, it would be beneficial to provide a monitoring system that is suitable for home use. Particularly valuable would be a system that is wireless and conveniently measures a collection of vital signs and hemodynamic parameters. Ideally, such a system would be easy to use, would improve measurement consistency, and feature a simple form factor that integrates into the patient's day-to-day activities. A monitoring system according to the invention, which facilitates monitoring a patient for HF, CHF, ESRD, cardiac arrhythmias, and other diseases, is designed to achieve this goal.

[0027]The inventive device and measurement methodologies are based in part on the discovery that the bio-impedance signals (e.g. TBI waveforms) used to determine vital signs and hemodynamic parameters can be measured over a conduction pathway that extends from the patient's wrist to a location on their thoracic cavity, e.g. their chest or belly button. (Additional conduction pathways we have discovered to be suitable include those that extend from the wrist to the torso, legs, opposing arm, or neck.) The form factor of the handheld device described herein accommodates such measurements with a system that is comfortable, easy to use, and includes re-usable electrodes to reduce costs. Measurements made by the handheld device suitably use the belly button as a ‘fiducial’ marker, as described in detail below. This location, which is present on nearly all patients, facilitates consistent, daily measurements that reduce errors due to positioning that normally impact impedance measurements. Other measurement locations, such as a nipple, mole or other birthmark, elbow, wrist joint, etc., may also be used as a fiducial marker. What is most important is that the patient positions the device consistently from one measurement to another. In this and other ways, the handheld device provides an effective tool for characterizing patients with chronic diseases, such as CHF, ESRD, and hypertension.

[0047]The measurement system described herein has many advantages. In particular, it features and easy-to-use device that a patient can use to measure all their vital signs, complex hemodynamic parameters, and basic wellness-related parameters. Such ease of use may increase compliance, thereby motivating patients to use it every day. And with daily use, the measurement system can calculate trends in a patient's physiological parameters, thereby allowing better detection of certain disease states and / or management of chronic conditions such as CHF, diabetes, hypertension, COPD, and kidney failure.

Problems solved by technology

TFC deviation in the day-to-day placement of the electrodes can result in measurement errors.

This, in turn, can lead to misinformation (particularly when trends of the measured parameters are to be extracted), thereby nullifying the value of such measurements and thus negatively impacting treatment.

Unfortunately, during a measurement, the lead wires can pull on the electrodes if the device is moved relative to the patient's body, or if the patient ambulates and snags the lead wires on surrounding objects.

Such pulling can be uncomfortable or even painful, particularly where the electrodes are attached to hirsute parts of the body, and this can inhibit patient compliance with long-term monitoring.

Moreover, these actions can degrade or even completely eliminate adhesion of the electrodes to the patient's skin, and in some cases completely destroy the electrodes' ability to sense the physiological signals at various electrode locations.

Chronic elevation of LVEDP causes transudation of fluid from the pulmonary veins into the lungs, resulting in shortness of breath (dyspnea), rapid breathing (tachypnea), and fatigue with exertion due to the mismatch of oxygen delivery and oxygen demand throughout the body.

As CO is compromised, the kidneys respond with decreased filtration capability, thus driving retention of sodium and water and leading to an increase in intravascular volume.

However, an extremely delicate balance between these two biological treatment modalities needs to be maintained, since an increase in blood pressure (which relates to afterload) or fluid retention (which relates to preload), or a significant change in heart rate due to a tachyarrhythmia, can lead to decompensated HF.

Unfortunately, this condition is often unresponsive to oral medications.

However, by itself, this parameter is typically not sensitive enough to detect the early onset of CHF—a particularly important stage when the condition may be ameliorated simply and effectively by a change in medication or diet.

These organs then respond with a reduction in their filtering capacity, thus causing the patient to retain sodium and water and leading to an increase in intravascular volume.

This, in turn, leads to congestion, which is manifested to some extent by a build-up of fluids in the patient's thoracic cavity (e.g. TFC).

CHF is also the leading cause of mortality for patients with ESRD, and this demographic costs Medicare nearly $90,000 / patient annually.

Less-than-satisfactory consistency with the use of any medical device (in terms of duration and / or methodology) may be particularly likely in an environment such as the patient's home or a nursing home, where direct supervision may be less than optimal.

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